1//===-- int_mulo_impl.inc - Implement __mulo[sdt]i4 ---------------*- C -*-===// 2// 3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4// See https://llvm.org/LICENSE.txt for license information. 5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6// 7//===----------------------------------------------------------------------===// 8// 9// Helper used by __mulosi4, __mulodi4 and __muloti4. 10// 11//===----------------------------------------------------------------------===// 12 13#include "int_lib.h" 14 15// Returns: a * b 16 17// Effects: sets *overflow to 1 if a * b overflows 18 19static __inline fixint_t __muloXi4(fixint_t a, fixint_t b, int *overflow) { 20 const int N = (int)(sizeof(fixint_t) * CHAR_BIT); 21 const fixint_t MIN = (fixint_t)((fixuint_t)1 << (N - 1)); 22 const fixint_t MAX = ~MIN; 23 *overflow = 0; 24 fixint_t result = (fixuint_t)a * b; 25 if (a == MIN) { 26 if (b != 0 && b != 1) 27 *overflow = 1; 28 return result; 29 } 30 if (b == MIN) { 31 if (a != 0 && a != 1) 32 *overflow = 1; 33 return result; 34 } 35 fixint_t sa = a >> (N - 1); 36 fixint_t abs_a = (a ^ sa) - sa; 37 fixint_t sb = b >> (N - 1); 38 fixint_t abs_b = (b ^ sb) - sb; 39 if (abs_a < 2 || abs_b < 2) 40 return result; 41 if (sa == sb) { 42 if (abs_a > MAX / abs_b) 43 *overflow = 1; 44 } else { 45 if (abs_a > MIN / -abs_b) 46 *overflow = 1; 47 } 48 return result; 49} 50